Chlorpheniramine exerts anxiolytic-like effects and activates prefrontal 5-HT systems in mice

Forced Swimming-Induced Depressive-like Behavior and Anxiety Are Reduced by Chlorpheniramine via Suppression of Oxidative and Inflammatory Mediators and Activating the Nrf2-BDNF Signaling Pathway

The first-generation antihistamine chlorpheniramine (CPA) is believed to have both anxiolytic and antidepressant properties. The current study sought to assess the mechanisms behind the antidepressant and anxiolytic effects of CPA therapy concerning oxidative stress, inflammation, and nuclear factor p45 for erythroid 2-Brain-derived neurotrophic factor (Nrf2-BDNF) signaling pathway in forced swimming-induced depressive-like behavior and anxiety. Eighteen male Wistar rats (180-200 gm) rats were separated into three groups (n = 6): a stressed group (acute stress) that underwent the forced swimming test (FST) and a stressed group that received pretreatment with CPA (10 mg/kg body weight) for 3 weeks (CPA + acute stress). Animals were subsequently put through the following behavioral tests after undergoing a forced swim test (FST) for 5 min: an immobility test, open field test, and elevated plus maze test. Serum cortisol levels were measured when the rats were euthanized at the end of the experiments. Brain neurotransmitters (cortisol, serotonin, and noradrenaline), oxidative stress (SOD and MDA), inflammatory (IL-6 and IL-1) biomarkers, and the Nrf2-BDNF signaling pathway in the hippocampus and cerebral cortex tissues was determined. CPA prevented stress-induced increases in cortisol levels (p < 0.0001), decreased brain neurotransmitters, and increased oxidative stress and inflammation. CPA also upregulated the Nrf2-BDNF signaling pathway. Thus, CPA mitigates depressive-like behavior and anxiety by inhibiting oxidative stress and inflammation and upregulating the Nrf2-BDNF signaling pathway in the brain tissues.

Acute elevated platform triggers stress induced hyperalgesia and alters glutamatergic transmission in the adult mice anterior cingulate cortex

Pain is composed of both physiological and affective/emotional components which potentiate one another. In addition, exposure to stress modulates pain and affective behaviors including, anxiety-like behavior and/or depression-like behaviors. Indeed, chronic exposure to stress has been known to enhance stress-induced hyperalgesia (SIH). The anterior cingulate cortex (ACC) is critically involved in pain sensation and emotions. Animal models of chronic pain, but not acute nociception have been found to induce synaptic plasticity on glutamatergic and GABAergic transmission in the rodent ACC. However, it is unclear whether acute stress exposure could produce SIH and cause synaptic plasticity in the ACC. Accordingly, we studied how acute exposure of stress by the elevated open platform (EOP) could affect mechanical threshold, thermal and cold latency in the adult mice. Thirty minutes of the EOP produced mechanical hypersensitivity lasting for 60 min and thermal hypersensitivity immediately after the exposure. Next, we tested whether the stress could alter the excitatory and inhibitory synaptic transmission in the ACC. We performed whole-cell patch-clamp recordings from layer II/III pyramidal neurons in the ACC and analyzed both glutamatergic and GABAergic transmission in mice following the EOP. Thirty minutes of the EOP altered the rise and decay time of spontaneous glutamatergic AMPA/GluK receptors mediated currents, but did not change the frequency or amplitude of excitatory transmission. By contrast, the kinetics of inhibitory synaptic currents were not altered by the EOP. These results suggest that acute stress by the elevated platform produces SIH and causes synaptic plasticity on excitatory transmission, but not inhibitory transmission in the ACC.

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

The reactivity of benzyl hypervalent iodine intermediates was explored in congruence with the reductive iodonio-Claisen rearrangement (RICR) to show that there may be an underlying mechanism which expands the reasoning behind the previously known C–C bond-forming reaction. By rationalizing the hypervalent iodine’s metal-like properties it was concluded that a transmetallation mechanism could be occurring with metalloid groups such as silicon and boron. Hypervalent iodine reagents such as Zefirov’s reagent, cyclic iodonium reagents, iodosobenzene/BF₃, and PhI(OAc)₂/BF₃ or triflate-based activators were tested. A desirable facet of the reported reaction is that iodine(I) is incorporated into the product thus providing greater atom economy and a valuable functional group handle for further transformations. The altering of the RICR’s ortho-selectivity to form para-selective products with benzyl hypervalent iodine intermediates suggests a mechanism that involves hypervalent iodine-guided electrophilic substitution (HIGES).

Chlorpheniramine and escitalopram: Similar antidepressant and nitric oxide lowering roles in a mouse model of anxiety

There is a crosstalk between mood disorders and oxidative stress. Chlorpheniramine (CPA), a first generation antihistamine, is hypothesized to have an anxiolytic role at high doses; however, its antidepressant and antioxidant roles have not previously been investigated. The aim of the current study was to evaluate the antidepressant and anxiolytic effects of CPA treatment in association with nitric oxide (NO) and super oxide dismutase (SOD) activity in a mouse model of anxiety. BALB/c mice were divided into unstressed (naïve), control, and CPA- (0.5 mg/kg) and escitalopram- (ESC; 10 mg/kg) treated groups for 3 weeks. Subsequently, they were immobilized for 6 h and subjected to behavioural paradigms as follows: The open field test, the elevated plus maze (EPM) and the forced swim test to investigate motor function, anxiety and depression, respectively. The mice were sacrificed and serum was obtained to detect NO and SOD activity. Compared with the control group, the CPA-treated group demonstrated an antidepressant effect similar to that of the ESC-treated group. In addition, CPA prevented stress-induced NO without affecting SOD activity. CPA did not improve anxiety-like behaviour in the EPM, nor did it improve stress-induced locomotion and rearing, as demonstrated by the OFT. Thus, to the best of our knowledge, this is the first study to evaluate the antidepressant role of CPA in association with NO metabolism. However, further studies are required to elucidate the underlying mechanism.

Intra-amygdala microinjections of chlorpheniramine impair memory formation or memory retrieval in anxiety- and fear-mediated models

H1 receptor histaminergic antagonist, chlorpheniramine (CPA) participates in cognitive performance in various animal models. However, little is known regarding the effects of CPA microinjection into the amygdala on emotional behavior. The purpose of this study was to investigate whether CPA microinjection into the amygdala has the same effect on two models, one anxiety- and the other fear-mediated, in various memory stages using the elevated plus maze (EPM) and the inhibitory avoidance task (IAT) tests. Two experiments were performed with seventy-two adult male Swiss mice. Behavioral testing was performed on two consecutive days, and in both experiments, before each trial, the animals received bilateral microinjections of saline (SAL) or CPA (0.16 nmol). The animals were re-exposed to the EPM or IAT 24h after the first trial. Four experimental groups were tested: SAL-SAL, SAL-CPA, CPA-SAL and CPA-CPA. In experiment 1, a decreased open arm exploration (% open arm entries, %OAE and% open arms time, %OAT) for SAL-SAL and SAL-CPA was showed, while these measures did not decrease for the CPA-SAL and CPA-CPA groups in Trial 2. In experiment 2, an increase of retention latency in relation to training 2 for the groups SAL-SAL and CPA-SAL and a significant decrease in latency for the group SAL-CPA was revealed. These results indicate that chlorpheniramine microinjection into the amygdala impairs emotional memory acquisition and/or consolidation in the EPM and retrieval of IAT.

Potentially inappropriate anticholinergic medication use in community-dwelling older adults: a national cross-sectional study

BACKGROUND

Inappropriate medications are often used in older adults despite their unfavourable risk-to-benefit profile. Although many of the medications in the American Geriatrics Society (AGS) Beers list are potentially inappropriate because of their anticholinergic properties, little is known regarding the nature and extent of potentially inappropriate anticholinergic medication use in older adults.

OBJECTIVES

To determine the prevalence of, and factors associated with, potentially inappropriate anticholinergic medication use in the older population.

METHODS

A retrospective, cross-sectional study was conducted, involving older adults (aged 65 years and older), using 2009-2010 Medical Expenditure Panel Survey (MEPS) data. The 2012 AGS Beers Criteria were used to define potentially inappropriate anticholinergic medications on the basis of the list of medications to avoid using in older adults irrespective of the diagnosis. Descriptive analyses were used to examine the nature and extent of potentially inappropriate anticholinergic medication use. Multivariable logistic regression within the conceptual framework of the Andersen Behavioral Model was used to identify the factors associated with potentially inappropriate anticholinergic use in older adults.

RESULTS

According to the MEPS, there were 78.60 million older adults in the USA; an estimated 7.51 million (9.56 %) of these older adults used potentially inappropriate anticholinergic medications in 2009-2010. The most frequently used potentially inappropriate anticholinergics were cyclobenzaprine, promethazine, amitriptyline, hydroxyzine and dicyclomine. Multivariable regression analyses revealed that female sex, residing in the South and the presence of anxiety disorder increased the likelihood of receiving potentially inappropriate anticholinergic medications, whereas older adults aged 75-84 or ≥ 85 years, and those with over 15 years of education, had a decreased likelihood of receiving potentially inappropriate anticholinergic medications.

CONCLUSION

The study found that approximately one in ten older adults used potentially inappropriate anticholinergic medications. Several predisposing, enabling and need factors were associated with the use of potentially inappropriate anticholinergic medications. Concerted efforts are needed to optimize potentially inappropriate anticholinergic medication use in older adults.

Investigation of Dose-Related Effects of Carnosine on Anxiety with Sympathetic Skin Response and T-maze

Carnosine is a dipeptide formed of the amino acids β-alanine and histidine. Only a limited number of studies have examined the effects of carnosine on sympathetic nerve activation and anxiety. The present study was undertaken to determine the dose-related effects of carnosine on anxiety in the elevated T-maze test (ETM) with electrodermal activity (EDA). Carnosine was injected in three groups of rats with doses of 10 (low dose), 100 (medium dose) and 1000 (high dose) mg/kg i.p. Physiological saline was injected in the sham group. The anxiety scores of the rats were measured with ETM 20 minutes after injection. Then, SCL was measured. The decreased number of entries into the open arm (NEOA), the percentage of time spent in the open arm (% TSOA) and higher EDA [shown by skin conductance level (SCL)] indicate higher anxiety. The NEOA and % TSOA were lower in the high-dose group than in the other groups. SCL was lower in the medium-dose carnosine group than in the high-dose carnosine and sham groups. SCL was higher in the high-dose group than in the medium-dose and sham groups. Our results suggest that high-dose carnosine produced anxiety-like effects as assessed in the SCL and ETM. Medium-dose carnosine acted as an anxiolytic. The anxiety-related responses of carnosine depend on its dose-related effect.

H₁ but not H₂ histamine antagonist receptors mediate anxiety-related behaviors and emotional memory deficit in mice subjected to elevated plus-maze testing

This study investigated the role of H₁ and H₂ receptors in anxiety and the retrieval of emotional memory using a Trial 1/Trial 2 (T1/T2) protocol in an elevated plus-maze (EPM). Tests were performed on 2 consecutive days, designated T1 and T2. Before T1, the mice received intraperitoneal injections of saline (SAL), 20 mg/kg zolantidine (ZOL, an H₂ receptor antagonist), or 8.0 or 16 mg/kg chlorpheniramine (CPA, an H₁ receptor antagonist). After 40 min, they were subjected to the EPM test. In T2 (24 h later), each group was subdivided into two additional groups, and the animals from each group were re-injected with SAL or one of the drugs. In T1, the Student t-test showed no difference between the SAL and ZOL or 8 mg/kg CPA groups with respect to the percentages of open arm entries (%OAE) and open arm time (%OAT). However, administration of CPA at the highest dose of 16 mg/kg decreased %OAE and %OAT, but not locomotor activity, indicating anxiogenic-like behavior. Emotional memory, as revealed by a reduction in open arm exploration between the two trials, was observed in all experimental groups, indicating that ZOL and 8 mg/kg CPA did not affect emotional memory, whereas CPA at the highest dose affected acquisition and consolidation, but not retrieval of memory. Taken together, these results suggest that H₁ receptor, but not H₂, is implicated in anxiety-like behavior and in emotional memory acquisition and consolidation deficits in mice subjected to EPM testing.

Olanzapine-induced hyperglycemia: possible involvement of histaminergic, dopaminergic and adrenergic functions in the central nervous system

BACKGROUND/AIMS

Atypical antipsychotic drugs such as olanzapine are known to induce metabolic disturbance. We have already shown that olanzapine induces hepatic glucose production through the activation of hypothalamic adenosine 5'-monophosphate-activated protein kinase (AMPK). However, it is unclear how olanzapine activates hypothalamic AMPK. Since olanzapine is known to antagonize several receptors, including histaminergic, muscarinic, serotonergic, dopaminergic and adrenergic receptors, we examined the effect of each receptor antagonist on blood glucose levels in mice. Moreover, we also investigated whether these antagonists activate hypothalamic AMPK.

METHODS

Male 6-week-old ICR mice were used. Blood glucose levels were determined by the glucose oxidase method. AMPK expression was measured by Western blotting.

RESULTS

Central administration of olanzapine (5-15 nmol i.c.v.) dose-dependently increased blood glucose levels in mice, whereas olanzapine did not change blood insulin levels. Histamine H1 receptor antagonist chlorpheniramine (1-10 μg i.c.v.), dopamine D2 receptor antagonist L-sulpiride (1-10 μg i.c.v.) and α1-adrenoceptor antagonist prazosin (0.3-3 μg i.c.v.) also significantly increased blood glucose levels in mice. In contrast, the blood glucose levels were not affected by muscarinic M1 receptor antagonist dicyclomine (1-10 μg i.c.v.) or serotonin 5-HT2A receptor antagonist M100907 (1-10 ng i.c.v.). Olanzapine-induced hyperglycemia was inhibited by the AMPK inhibitor compound C, and AMPK activator AICAR (10 ng to 1 μg i.c.v.) significantly increased blood glucose levels. Olanzapine (15 nmol), chlorpheniramine (10 μg), L-sulpiride (10 μg) and prazosin (3 μg) significantly increased phosphorylated AMPK in the hypothalamus of mice.

CONCLUSION

These results suggest that olanzapine activates hypothalamic AMPK by antagonizing histamine H1 receptors, dopamine D2 receptors and α1-adrenoceptors, which induces hyperglycemia.

Dextromethorphan, chlorphenamine and serotonin toxicity: case report and systematic literature review

The aim of this review was to describe a patient with serotonin toxicity after an overdose of dextromethorphan and chlorphenamine and to perform a systematic literature review exploring whether dextromethorphan and chlorphenamine may be equally contributory in the development of serotonin toxicity in overdose. A Medline literature review was undertaken to identify cases of serotonin toxicity due to dextromethorphan and/or chlorphenamine. Case reports were included if they included information on the ingested dose or plasma concentrations of dextromethorphan and/or chlorphenamine, information about co-ingestions and detailed clinical information to evaluate for serotonin toxicity. Cases were reviewed by two toxicologists and serotonin toxicity, defined by the Hunter criteria, was diagnosed when appropriate. The literature was then reviewed to evaluate whether chlorphenamine may be a serotonergic agent. One hundred and fifty-five articles of dextromethorphan or chlorphenamine poisoning were identified. There were 23 case reports of dextromethorphan, of which 18 were excluded for lack of serotonin toxicity. No cases were identified in which serotonin toxicity could be solely attributed to chlorphenamine. This left six cases of dextrometorphane and/or chlorphenamine overdose, including our own, in which serotonin toxicity could be diagnosed based on the presented clinical information. In three of the six eligible cases dextromethorphan and chlorphenamine were the only overdosed drugs. There is substantial evidence from the literature that chlorphenamine is a similarly potent serotonin re-uptake inhibitor when compared with dextrometorphan. Chlorphenamine is a serotonergic medication and combinations of chlorphenamine and dextromethorphan may be dangerous in overdose due to an increased risk of serotonin toxicity.

Dextromethorphan, chlorphenamine and serotonin toxicity: case report and systematic literature review

The aim of this review was to describe a patient with serotonin toxicity after an overdose of dextromethorphan and chlorphenamine and to perform a systematic literature review exploring whether dextromethorphan and chlorphenamine may be equally contributory in the development of serotonin toxicity in overdose. A Medline literature review was undertaken to identify cases of serotonin toxicity due to dextromethorphan and/or chlorphenamine. Case reports were included if they included information on the ingested dose or plasma concentrations of dextromethorphan and/or chlorphenamine, information about co-ingestions and detailed clinical information to evaluate for serotonin toxicity. Cases were reviewed by two toxicologists and serotonin toxicity, defined by the Hunter criteria, was diagnosed when appropriate. The literature was then reviewed to evaluate whether chlorphenamine may be a serotonergic agent. One hundred and fifty-five articles of dextromethorphan or chlorphenamine poisoning were identified. There were 23 case reports of dextromethorphan, of which 18 were excluded for lack of serotonin toxicity. No cases were identified in which serotonin toxicity could be solely attributed to chlorphenamine. This left six cases of dextrometorphane and/or chlorphenamine overdose, including our own, in which serotonin toxicity could be diagnosed based on the presented clinical information. In three of the six eligible cases dextromethorphan and chlorphenamine were the only overdosed drugs. There is substantial evidence from the literature that chlorphenamine is a similarly potent serotonin re-uptake inhibitor when compared with dextrometorphan. Chlorphenamine is a serotonergic medication and combinations of chlorphenamine and dextromethorphan may be dangerous in overdose due to an increased risk of serotonin toxicity.